1. Field of the Invention
This invention relates to a thermosetting urethane elastomer, more particularly to a thermosetting urethane elastomer prepared from a prepolymer containing isocyanate groups at terminal ends obtained from p-phenylene diisocyanate (hereinafter abbreviated as PPDI) and a polyol and a curing agent comprising specific polyols.
2. Related Background Art
Thermosetting urethane elastomers are generally produced according to (a) the method in which a prepolymer contaInIng Isocyanate groups at terminal ends derived from a diisocyanate such as tolylene diisocyanate, diphenylmethane diisocyanate (hereinafter abbreviated as MDI), hexamethylene diisocyanate, etc. and a polyol such as polyether polyol, polyester polyol or polycaprolactone polyol, etc. is cured with a curing agent of a glycol such as 1,4 -butylene glycol (hereinafter abbreviated as 1,4-BG) or an amine such as 3,3'-dichloro-4,4'-diaminodiphenyl-methane, or (b) the method in which an unstable prepolymer derived from 1,5-naphthalene diisocyanate (hereinafter abbreviated as NDI) and a polyester polyol is rapidly cured with a glycol such as 1,4-BG, etc.
These thermosetting urethane elastomers are highly elastic, having excellent tensile strength, etc., and have been widely used for rolls, solid tires, belts, etc. However, the elastomer obtaIned in the above method (a) is inferior in heat resistance to be greatly changed in hardness depending on the temperature, and therefore unsuitable for use in a place which becomes elevated temperature or a place where the temperature is greatly changed. On the other hand, the prepolymer obtained in the above method (b) is excellent in heat resistance, but since an unstable prepolymer is used, drawbacks are involved in equipment during production and restriction in time.